Picosecond transient orientational and concentration gratings in germanium

• Published in: IEEE journal of quantum electronics Vol. 19; no. 4; pp. 690 - 700
• Main Authors: Smirl, A., Boggess, T., Wherrett, B., Perryman, G., Miller, A.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-04-1983; Institute of Electrical and Electronics Engineers
• Subjects: Anisotropic magnetoresistance; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Delay; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Germanium; Gratings; Impact phenomena (including electron spectra and sputtering); Laser-beam impact phenomena; Optical polarization; Optical pulses; Physics; Probes; Pulse measurements; Pulse modulation; Diffraction grating; Semiconductor materials; Laser beam; Modulation; Charge carrier; Unsteady state; Photoinduced effect; Germanium; Optical pulse; Orientation; Energy level population
• ISSN: 0018-9197; 1558-1713
• DOI: 10.1109/JQE.1983.1071920

We present and discuss the results of picosecond transient grating self-diffraction measurements in germanium that can be understood in terms of an orientational grating produced by anisotropic (in k space) state-filling. Although there have been predictions and indirect experimental evidence for isotropic state-filling in germanium, this is the first direct experimental indication of anisotropic state-filling in a semiconductor. We compare the self-diffracted signals from orientational gratings with those from band-filling induced concentration gratings and find several distinctions, all of which can be explained in terms of the theory developed in the preceding paper. In addition, we have performed three-pulse transient grating lifetime measurements which indicate that the concentration grating decay is tens of picoseconds, while the orientational grating decay is too rapid to resolve with our 8 ps pulses.